1. Field
Various aspects of the disclosed approach relate generally to communications systems, and more particularly, to rate control in wireless communications systems that take into account effective aggregation size.
2. Background
Wireless communications technology has penetrated nearly every aspect of a person's daily routine. Integrated into almost every conceivable electronic device to facilitate business activities as well as personal uses such as entertainment, medicine, and exercise, wireless communications systems are widely deployed to provide various types of content such as voice, data, video, and so on. For example, one type of wireless communications system, referred to as a wireless local area network (WLAN), has become commonplace for wirelessly linking one more devices to a local area network for communicating with other networked devices or to each other in an ad-hoc configuration. These devices may also connect to a device referred to as an access point for access to the wider Internet. Most WLANs are based on a set of WLAN protocols as promulgated by the Institute of Electrical and Electronic Engineers (IEEE) that provides a set of standards which allow manufacturers that follow them to build interoperable wireless devices. Just as importantly, these standards provide a framework for wireless devices to operate under a variety of environments, and users benefit because they have mobility to move around within a local coverage area and still have their wireless devices be connected to the network.
Of course, as the user moves with the wireless device from one location to another, the wireless device will experience an impact to its ability to communicate at a particular data rate via a communications link due to a variety of factors. For example, physical layer (PHY) transmission properties, media access control layer (MAC) protocols, and environmental factors may all impact reliability and throughput of communications on the communications link. Thus, when the communications link suffers from increased noise and/or interference, lower data rates may have to be used to ensure a particular data rate is achieved. Conversely, when the communications link experiences improved link conditions, higher data rates may be communicated reliably.
Typically, a set of communications profiles are predefined between wireless devices so as to limit an amount of overhead that may need to communicated before a communications link is establish, such as information about what parameters are being used for each transmission. Each communications profile in the set of communications profiles typically stores a different version of the parameters, where each version is customized to achieve a particular data rate under a variety of conditions. For example, each communications profile may have associated PHY transmission or MAC protocol property options that may maximize throughput under a particular link condition. Although no particular data rate can be guaranteed over all conditions, it is expected that more robust communications profiles may provide a higher probability of successful transmissions, albeit at a lower data rate. Thus, the set of communications profiles may include communications profiles that support a range of data rates. A particular communications profile may then be selected based on a desired data rate.
For example, consider a situation where a transmitting device uses a first communications profile to communicate at a first data rate to a receiving device over a communications link. At a particular point during a series of transmissions over the communications link, if the transmitting device determines from feedback by the receiving device that the communications link is suffering from a sufficient level of interference that will not allow the current, first data rate to be sustained, then the transmitting device may adjust the data rate for future transmissions simply by selecting another predefined communications profiles from the set of communications profiles. In general, the process of choosing a particular communications profile in an attempt to achieve an optimized data rate for a particular link condition is referred to as “data rate control,” or “rate control” for short. The process may also be known as “rate adaptation.”
As communications technology has evolved, the number of options available for dealing with different types of link conditions has increased. For example, the set of communications profiles may be configured with communications profiles having various orthogonal frequency division multiplexing (OFDM) modulation techniques, enhanced modulation and coding schemes (MCS), and/or multiple-input multiple-output (MIMO) antenna configurations. However, although many possible communications profiles may be available in the set of communications profiles, current approaches for communications profile selection during rate control are not optimized, and may unnecessarily limit an actual amount of data a wireless device could communicate.
In order to be able to support increased data rates by optimizing rate control techniques, other approaches are desired.